I found some small mistakes which you might correct.
I hope this will help you a little.
There should be no compulsory school subjects. Students should be allowed to choose the subjects they want to study. Do you agree?
There are many different subjects in school. Most of them are compulsory. Students have to learn them, even if they are not interested. Perhaps they should be allowed to choose subjects that they want to study.
On (no the) one hand I think that subjects shouldn’t be compulsory in (no the) high school because people should concentrate on the subjects that will be useful (no in) for them in the future. For example. for a person who wants to study Polish philology, maths or physics may not be important.
On the other hand, young people usually don’t know what they will do in the future, so it can be very difficult for them to make a choice. They have to learn all subject for a few years to have a possibility to choose some of them. Moreover, people need to have general knowledge about the world. It is good to know at least some basic things about everything.
To sum up, I think that students should be allowed to choose the subjects they want to study and concentrate on them especially at high school. At primary and secondary school students should learn all subjects to discover what is interesting for them.
Maybe you could start explaining how it works in your country, then describe the possibilities (as you did in your essay), and after that give your opinion.
Student or Learner